After the first stone is laid late this year it will become one of Europe's biggest building sites, creating tens of thousands of jobs in recession-hit Spain, as a vast complex of hotels, casinos and conference centres – possibly complete with a replica of New York's Times Square – emerges from dusty fields outside Madrid.

But on Friday, just as multibillionaire Sheldon Adelson's Las Vegas Sands corporation announced that it now had the €9.8bn (£8.3bn) financing needed to start building Europe's biggest casino and conference centre, protesters were claiming the 36,000-hotel-room complex would bring gambling addiction and prostitution to Spain's capital.

"There should be no concern about this company's ability to have the financing and the money. We have it," said Adelson's number two, Michael Leven, as he announced that the company had chosen a site in the dormitory town of Alcorcón.

He said Las Vegas Sands would find $3.6bn from its own resources and had banks lined up to lend the rest. Sources close to the company said it was too early to sign agreements with the banks, as a public tender process by the Madrid regional government had to be carried out first.

Radio stations immediately buzzed with talk about the arrival of Adelson – the man behind the Venetian and Palazzo hotels in Vegas and other vast casino complexes in Macau and Singapore – and of the tens of thousands of jobs the project should create in a country with 26% unemployment and an economy shrinking at an annual 1.8%.

The first, $9.8bn stage of the project – with four separate "resorts" of 3,000 hotel rooms with casino facilities attached – is due to open in 2017.

That will be just the first phase of transforming the three square mile site into a gambling and conference city crowned by a 72-storey hotel building that will become the biggest in the region – looming over the neighbouring campus headquarters of Santander bank.

By that stage the so-called EuroVegas complex will have tripled in size to house 12 resorts with half a dozen casinos, a convention centre, three golf courses, theatres, shopping malls, bars and restaurants. "I think it will be very exciting for everyone," said Leven, who added that Adelson, 79, hoped to see it completed before his 100th birthday.

Sources close to the company claimed that, when the entire project is finished in 18 years, some 240,000 direct and indirect jobs would be created.

"We are building four resorts in the first phase, with approximately 3,000 bedrooms in each resort and the attendant facilities," said Leven, who compared the job-creating capacity to the company's projects in Singapore and Macau. "Singapore, which is about the same size as one of these [12 eventual resorts], employs approximately 10,000 people directly and 10,000 more indirectly."

ABC newspaper ran pictures from the EuroVegas project it claimed had been presented to local government officials by the company, showing two Shard-like twin skyscrapers said to be 250 metres tall that appear to represent one of the "resorts". The complex will reportedly also include a copy of New York's Times Square.

The announcement comes after years of negotiations and saw the Madrid regional government announce what appeared to be a made-to-measure public tender. The tender process was set to be completed by September, officials said.

Madrid's regional president Ignacio Gonzalez also virtually promised that Spain's central government would deliver the tax changes, infrastructure and even exemptions to the no-smoking laws that Adelson sought. "On the tax side everything is resolved, though some changes from central government are awaited," he said. "The smoking issue is also a matter for central government. It is working on it and will come up with a solution in the next few months, with a chance for restricted smoking."

Government officials later denied that they planned to change no-smoking laws but protesters claimed that the government was creating a special low-tax "mini-state" for Adelson.

"Citizens have never been consulted about this," the EuroVegas No platform said in a statement. "The most probable thing is that EuroVegas provides profits for a very few while causing irreversible environmental damage."

"This project is not just about gambling, but is an integral resort," said Gonzalez, highlighting the conference centre, shopping malls, theatres and other leisure facilities at the site.

While Adelson's Las Vegas resorts now take in more money from non-gambling activities, the ones in Singapore and Macau are very dependent on their casinos.

Gonzalez said that Madrid, which recently built a new terminal at the airport, had enough air capacity to handle the one million tourists from around Europe who would be expected to visit.

Adelson hopes EuroVegas will become a magnet for conferences and gamblers from around the continent — just as his casinos and resorts in Macau cater for a vast Chinese market.

Las Vegas-based Adelson is the 12th richest person in the United States, according to Forbes — which gives his net worth as $20.5bn. He received a $2.9bncash bonus from his company earlier this year.

Adelson was a key Republican backer in the last presidential elections and is reported to be financing a campaign to prevent President Barack Obama nominating Chuck Hagel as defence secretary.